Antimicrobial treatment of textile materials

ABSTRACT

Antimicrobial treatment of textile material with an oligomeric or polymeric biguanide and a strong organic acid having a pK value below 4.5. Acid protects treated material against yellowing the presence of chlorine bleaches and loss of antimicrobial activity on laundering. The preferred biguanide is poly(hexamethylene biguanide) hydrochloride.

This application claims benefit of international applicationPCT/GB94/02184, filed Oct. 7, 1994.

The present invention relates to textile materials which are treatedwith a biguanide and a strong organic acid to prevent yellowing and lossof antimicrobial activity when subsequently laundered with an anionicdetergent containing hypochlorite bleach.

It has been proposed to treat textile materials with poly(hexamethylenebiguanide) in order to confer antimicrobial properties to the textilematerial as disclosed in EP 136 900.

Biguanides are particularly suited to application to textiles,especially cellulosic textiles and blends thereof, because of thesubstantivity which biguanides exhibit for such materials. However, suchapplications have not become commercially established where the treatedmaterial is to be subjected to laundering. There are two major reasonsfor this. Firstly, many commercially available detergents containchlorine bleaching agents which react with the biguanide groups toproduce a yellow discoloration and cause loss of antimicrobialprotection. This is a particular disadvantage in white or pale colouredtextiles. Secondly, many commercial detergents contain anionicsurfactants which complex with the biguanide groups which often producesticky deposits resulting in loss of "handle" and often impair thestain-release properties of the textile material. Also, followinglaundering, the textile material often exhibits an increase tendency to"tendering".

It has now been found that some or all of these deficiencies may beovercome by treating the textile material with a biguanide and anorganic acid.

According to the invention, there is provided a method of treating atextile material to inhibit microbial growth which comprises applying tothe textile material a) an oligo- or polymeric biguanide or the saltthereof with an inorganic acid or an organic acid having a pK valueabove 4.5 (hereafter "biguanide") and b) a strong organic acid having apK value below 4.5 and free from any aliphatic or oxyalkylene chaincontaining 12 or more carbon atoms (hereafter "strong organic acid").

The biguanide which is used to treat the textile material contains atleast two biguanide units of the formula (I): ##STR1## and preferablyfrom 2 to 100 such biguanide units.

Typically the biguanide units are linked by a bridging group whichincludes at least one methylene group. The bridging group may include apolymethylene chain which may optionally be interrupted by hetero atomssuch as oxygen, sulphur or nitrogen. The bridging group may include oneor more cyclic nuclei which may be saturated or unsaturated. It isgenerally preferred that the bridging group is such that there are atleast three, and especially at least four, carbon atoms directlyinterposed between adjacent units of the formula (I). In general it ispreferred that there are not more than ten carbon atoms and, especiallynot more than eight carbon atoms interposed between two adjacent unitsof the formula (I).

The terminal biguanide units may themselves be terminated by anysuitable terminating group such as hydrocarbyl, substituted hydrocarbylgroup, amino or amine hydrochloride or a group ##STR2## If theterminating group is hydrocarbyl this may be alkyl, cycloalkyl or arylor a combination thereof, such as aralkyl. If the terminating group issubstituted hydrocarbyl, the substituent or substituents can be anygroup or groups which do not have art undesirable adverse effect on theantimicrobial activity of the biguanide such as a hydrocarbyloxy,hydrocarbylcarbonyl (i.e. acyl), an ester (i.e. acyloxy), halogen atomor CN.

The biguanide may comprise a single species, especially where this is adimer, or a mixture of species especially where it is polymeric andcomprises a mixture of polymers having different chain lengths.

One preferred biguanide is a dimer which contains two units of theformula (I) linked by a polymethylene group, particularly ahexamethylene group. The terminating groups of preferred dimers are##STR3## 4-chlorophenyl or 2-ethylhexyl, for example as in the compoundof formulae (IIa) and IIb, respectively ##STR4##

Another preferred biguanide comprises a mixture of polymeric biguanides,especially a mixture of linear polymeric biguanides with a recurringpolymer unit represented by the formula ##STR5## wherein X and Y may bethe same or different and represent bridging groups in which the totalnumber of carbon atoms directly interposed between the pairs of nitrogenatoms linked by X and Y is at least 9 and not more than 17.

The bridging groups X and Y may be polymethylene chains, optionallyinterrupted by hetero atoms such as oxygen, sulphur or nitrogen. X and Ymay also incorporate cyclic nuclei which may be saturated orunsaturated, in which case the number of carbon atoms directlyinterposed between the pairs of nitrogen atoms linked by X and Y istaken as including the shortest segment or segments of the cyclic groupor groups. Thus, the number of carbon atoms directly interposed betweenthe nitrogen atoms in the group ##STR6## is 4 and not 8.

The preferred biguanide for use in the present invention ispoly(hexamethylene biguanide), in which X and Y both represent the--(CH₂)₆ -- group.

The mixture of polymeric biguanides may be prepared by the methodsdescribed in UK Patent Specification Nos. 702,268 and 1,152,243respectively, and any of the biguanide species or mixtures thereofdescribed therein may be used as the biguanide in the present invention.

The polymeric biguanides may be terminated by an amine hydrochloridegroup or by an ##STR7## group, and the terminating groups on eachpolymer chain may be the same or different.

In any mixture of polymeric biguanides the number of individualbiguanide units, i.e. ##STR8## is preferably from 3 to about 80.

A preferred biguanide is a mixture of poly(hexamethylene biguanides) offormula III in the form of their hydrochloride salts. ##STR9## wherein nis from 4 to 15. The average molecular weight of this mixture ofpolymeric biguanides is from about 1100 to about 3300.

A preferred mixture of polymeric biguanides is available as an aqueousconcentrate supplied as VANTOCIL IB (ZENECA Ltd). Poly(hexamethylenebiguanide) hydrochloride is hereinafter referred to as PHMB.

The biguanide is preferably applied to the textile material as a salt ofan inorganic acid or weak organic acid having a pK value above 4.5(hereafter "weak organic acid"), especially a monobasic inorganic orweak organic acid. Examples of inorganic acids are hydrohalic acids suchas the hydrobromic acid and especially hydrochloric acid. Examples ofweak organic acids are acetic and propionic acids.

The strong organic acid may itself have antimicrobial activity, but thisis not essential to the working of the invention. It may be a sulphonicacid or a sulphate but is preferably a carboxylic acid. The organic acidmay contain more than one acid group such as in di- and tri-carboxylicacids and polymers and co-polymers derived from acrylic and methacrylicacid.

The strong organic acid may be substituted or unsubstituted. When it issubstituted, the substituent or substituents may be any atom or groupwhich reduces the pK value relative to the unsubstituted acid providedthat such atom or group does not significantly affect the antimicrobialproperties of the treated textile material and that it provides therequired resistance to laundering. In the context of the invention,sulphamic acid is to be regarded as a strong organic acid.

Preferred strong organic acids are those containing 2 or 3 carboxylicacid groups.

The strong organic acid is essentially devoid of surface activeproperties and has little or no detergency properties. It is alsoessentially non-foaming.

The strong organic acid preferably has a pK value less than 4.0, morepreferably less than 3.5 and especially from 3.1 to 0.5.

The acid group or groups of the strong organic acid are preferably--COOH, --CSOH or --COSH although in the following generic formulae IV,V and VI such groups are represented as --COOH for convenience. It ispreferred that each acidic group is carboxy i.e. --COOH.

One preferred strong organic acid has the formula IV ##STR10## wherein Ris halogen, C₁₋₆ -alkyl, C₁₋₆ -alkenyl, substituted C₁₋₆ -alkyl, phenyl,substituted phenyl, nitrile, carboxy, a group OR³ or a group R³ CO.

R¹ and R² are, independently, hydrogen, halogen, amino, substitutedamino, hydroxy, C₁₋₆ -alkyl, substituted C₁₋₆ -alkyl or R and R¹together with the carbon atom to which they are attached form analicyclic or heterocyclic ring; and

R³ is C₁₋₆ -alkyl, substituted C₁₋₆ -alkyl, phenyl or substitutedphenyl; provided that R, R¹ and R² are selected to give a pK value below4.5.

Another preferred strong organic acid has the formula V ##STR11##wherein R⁴ is hydrogen, C₁₋₆ -alkyl, substituted C₁₋₆ -alkyl C₁₋₆-alkenyl, phenyl substituted phenyl or --COOH; and

R⁵ and R⁶ are, independently, hydrogen, C₁₋₄ -alkyl or substituted C₁₋₄-alkyl.

A further preferred strong organic acid has formula VI

    R.sup.7 --COOH                                             VI

wherein

R⁷ is phenyl, substituted phenyl or the group --COOH.

When R, R¹ or R² is halogen, it is preferably iodine, fluorine, bromineor more especially chlorine.

When R, R¹, R² or R³ is alkyl, it may be linear or branched, but ispreferably linear.

When R to R⁶ is substituted alkyl, the substituent or substituents ispreferably hydroxy, halogen, amino, substituted amino, nitrile, carboxyor R⁸ CO-- where R⁸ is C₁₋₄ -alkyl or phenyl.

When R¹ or R² is substituted amino, the substituent is preferably C₁₋₄-alkyl or the group R⁸ --CO.

When R, R³, R⁴ or R⁷ is substituted phenyl, the substituent ispreferably C₁₋₄ -alkyl, hydroxy, halogen, nitro or --COOH.

When R and R¹ together with the carbon atom to which they are attachedform an alicyclic ring, it is preferably cyclohexyl or cyclopropyl.

When R and R¹ together with the carbon atom to which they are attachedform a heterocyclic ring, it is preferably furanyl.

Examples of the strong organic acid of formula IV wherein R¹ is amino orsubstituted amino are aspartic acid, leucine, phenylalanine and hippuricacid.

Organic acids of formula IV which have been found particularly usefulare those containing two or more carboxylic acid groups, especiallythose also containing one or two hydroxy groups i.e. wherein one or bothof R¹ and R² is hydroxy. Examples of such acids are adipic, butanetetracarboxylic, citric, dihydroxymalic, dihydroxytartaric,dimethylmalic, dimethylmalonic, glutaric, itaconic, malic, malonic,methylglutaric, methylmalonic, methylsuccinic, suberic, succinic,tartronic and tartaric acid.

Examples of monocarboxylic organic acids of formula IV are acetoacetic,ascorbic, bromoacetic, chloroacetic, chlorobutyric, chlorophenoxyacetic,chlorophenylacetic, chloropropionic, cyanoacetic, cyanophenoxyacetic,cyanopropionic, dichloroacetic, dichloroacetylacetic, diphenylacetic,ethylphenylacetic, glycolic, hydroxypropionic, iodoacetic, lactic,mandelic, nitrophenylacetic, nitrophenylpropionic, phenylacetic,phenylpropionic, trichloroacetic and vinylacetic acid.

Examples of organic acids of formula IV where R and R¹ form an alicyclicring are cyclohexane-1,1-dicarboxylic and cyclopropane-1,1-dicarboxylicacids.

Examples of organic acids of formula V are acrylic, chlorocinnamic,fumaric, maleic, mesaconic, methylcinnamic and sorbic acid.

Examples of acids of formula VI are benzoic, bromobenzoic,chlorobenzoic, dihydroxybenzoic, ethylbenzoic, hydroxybenzoic,iodobenzoic, trimethylbenzoic, o-phenylbenzoic, phthalic,isopropylbenzoic, terephthalic, toluic acid and oxalic acid.

Examples of thiocarboxylic acids are thioacetic, thiomalic, thioglycolicand thiolactic acids.

Particularly useful effects have been obtained with citric, maleic,malonic and especially oxalic acids.

The textile material may be of natural or synthetic fibres includingblends thereof. Thus, it may be cellulose, including viscose rayon andregenerated viscose rayon, wool, acrylic, polyamide such as nylon,polyester such as polyethyleneglycolterephthalate or polyurethane. Itis, however, preferably cellulose or blends thereof.

The textile material may be woven or knitted or may be in the form ofdry or wet laid fibres. It may be in the form of sheets, webs, threadsor ready made up garments such as drapes, shirting, toweling, underwear,socks and sheeting. The textile material is especially that which maybecome soiled and prevalent to microbiological growth thus giving riseto objectionable odours or to health/hygiene problems.

The biguanide may be the only antimicrobial agent applied to the textilematerial or a mixture of such biguanides may be used. Otherantimicrobial agents may also be included to improve the spectrum ofmicrobiological protection provided that such other antimicrobial agentdoes not significantly interfere with the improved resistance of thetreated textile material to laundering.

The textile material may also contain other textile processing adjuvantssuch as binders or resins, especially phenolformaldehyde or urea-glyoxalresins which are commonly used in the trade to impart crease-resistanceand "easy care" properties to the textile material.

The biguanide is preferably applied to the textile material before thestrong organic acid is applied. The biguanide and strong organic acid mybe applied by any process common to the textile imdustry which isappropriate to the actual textile material. Thus, application may be bybatch or substantive exhaustion, padding, dipping or spraying. Whereappropriate, the textile material may be dried after application of thebiguanide and prior to the application of the strong organic acid. Thetextile material may be white or coloured with either dyestuffs orpigments. It may contain other textile adjuvants commonly used intextile finishing processes such as brightening agents and softeners.

Since the biguanide in the form of a salt with an inorganic acid or weakorganic acid is water soluble, the biguanide is preferably applied fromaqueous solution. However, the solution of biguanide may contain otherhydrophilic compounds or co-solvents such as ethanol. Similarly, thestrong organic acid is also preferably applied from aqueous solutioneither in the form of the free carboxylic acid or in the form of awater-soluble salt, especially alkali metal salt such as lithium, sodiumor potassium salt or as an ammonium salt.

The amount of biguanide which is applied to the textile material may bejust sufficient to confer an antimicrobial effect to the material but ispreferably in excess of this amount. Generally, the amount of biguanideis up to 2% preferably up to 1%, more preferably up to 0.5% andespecially up to 0.1% by weight of the textile material. Goodantimicrobial effects have been obtained with up to 0.01% by weight oftextile material.

For convenience, an excess of the strong organic acid is applied so thatthose biguanide groups which are not required to bind with the textilematerial are blocked by the strong organic acid. Any excess of the acidmay be removed by rinsing with water, but this is generally notnecessary. It is particularly preferred that the amount of strongorganic acid is just sufficient to form a salt with all the biguanidegroups not required to bind with the textile material.

The textile material containing the biguanide which has been treatedwith the strong organic acid shows reduced tendency to discolour whenexposed to a chlorine-containing bleach and also retains antimicrobialactivity after washing with an anionic detergent. It has been found thatcertain textile materials, especially cellulosic materials retainantimicrobiological activity even after repeated laundering cycles. Inaddition, the textile materials treated according to the inventionretain similar "handle" and "soil-release" characteristics afterlaundering compared with that of the untreated material.

Thus, as a further aspect of the invention there is provided a textilematerial treated with an oligo- or polymeric biguanide and a strongorganic acid having a pK value below 4.5 and free from any aliphatic oroxyalkylene chains containing more than 12 carbon atoms. Some of thesalts formed on the textile material are believed novel. Thus, as astill further aspect of the invention there is provided a salt ofpoly(hexamethylene biguanide) and a strong organic acid having a pKbelow 4.5 and free from any aliphatic or oxyalkylene chains containingmore than 12 carbon atoms.

The invention is now further described with reference to the followingexamples where the amounts are expressed as parts by weight unlessexpressed to the contrary.

EXAMPLES 1 TO 17

These examples illustrate the protection against yellowing.

5 cm² squares of white cotton woven cloth (0.25 parts) were immersed ina 0.1% aqueous solution of PHMB for 5 minutes at 20°-25° C. The cottonwas then removed and rinsed thoroughly with water. The treated cottonwas then immersed in a 1% aqueous solution of a strong organic acid for5 minutes at 20°-25° C. and again removed, squeezed and rinsed withwater. The cotton pieces were finally immersed in a 3% aqueous solutionof sodium hypochlorite at 40° C. for 1 hr. Again the cotton pieces weresqueezed and thoroughly rinsed in water before drying.

The colour of these samples was assessed visually by measuring thecolour with a Macbeth Reflectance Spectrophotometer. The results aregiven in Table I below.

                  TABLE 1                                                         ______________________________________                                        Example a Comp Ex                                                                        Organic Acid pK      Whiteness (a) %                               ______________________________________                                        1          citric       2.9     100                                           2          lactic       3.7     97.0                                          3          glycolic     3.6     98.7                                          4          thioglycolic 3.4     99.9                                          5          thiolactic   3.5     99.6                                          6          ethoxyacetic 3.5     98.5                                          7          chloroacetic 2.7     101.9                                         8          tartaric     2.8     98.9                                          9          malic        3.2     97.6                                          10         benzoic      4.0     ND                                            11         aspartic     1.9     90.0                                          12         phenylalanine                                                                              2.2     89.7                                          13         leucine      2.4     89.5                                          14         oxalic       1.1     100                                           15         malonic      2.6     99.3                                          16         maleic       1.7     96.8                                          17         btca         3.4     99.8                                          A          acetic       4.5     yellow                                        B          2-hydroxybutyric                                                                           4.7     yellow                                        C          3-hydroxybutyric                                                                           4.72    yellow                                        D          4-hydroxybutyric                                                                           4.72    yellow                                        E          boric                yellow                                        Control    --           --      73                                            ______________________________________                                         Fotenote to Table                                                             btca is butane tetracarboxylic acid                                           a) Whiteness is measured as percent reflectance against a piece of            untreated cotton.                                                             ND is not determined.                                                    

EXAMPLE 18

This illustrates the antimicrobial properties of treated cotton.

A phosphate buffer as prepared by mixing aqueous solutions of 0.2mol/liter Na₂ HPO₄ (72 ml) and 0.2 mol/liter NaH₂ PO₄ (28 mls), addingNaCl (5 parts) and diluting to 1 liter with distilled water. This buffersolution was sterilised by heating at 121° C. for 15 minutes.

A 24 hour shaken culture of Staphylococcus aureus (ATCC 6538P) wasprepared at 37° C. The cell concentration was measured using ahaemocytometer and the culture diluted with the phosphate buffersolution to give a concentration of between 5E5 and 3E5 cfu/ml (E islogarithmic power to base 10).

Samples of cotton cloth (0.2 parts) to be tested were placed in ascrew-necked flask, inoculated with 0.2 ml of the bacterial culture, andthe flask sealed and incubated at 37° C. for 18 hours.

After incubation, 20 mls of the phosphate buffer solution were added andthe flask shaken for about 1 minute. The concentration of survivingcells in the buffer solution was then determined by a standard serialdilution technique on nutrient agar after 24 hour incubation at 37° C.The results are detailed in Table 2 for cotton samples treated withcitric acid alone, PHMB alone and both citric acid and PHMB both withand without bleach. The treatment with citric acid, PHMB and bleach isas described in Example 1. The results show that citric acid preventsyellowing but exhibits poor antimicrobial activity and that thecombination of citric acid and PHMB retains antimicrobial activity andalso protects against yellow discoloration in the presence ofhypochlorite bleach.

                  TABLE 2                                                         ______________________________________                                        Example or       organic                Surviving                             Comp Ex biguanide                                                                              acid     bleach                                                                              Appearance                                                                            bacteria                              ______________________________________                                        Control none     none     no    white   6E3                                   F       none     none     yes   white   7E3                                   G       none     1% citric                                                                              no    white   6E2                                   H       0.01%    none     yes   yellow  0                                             PHMB                                                                  18      0.01%    1% citric                                                                              yes   white   0                                             PHMB                                                                  ______________________________________                                    

EXAMPLE 19

This example illustrates the durability of the antimicrobial activity torepeated laundering. Samples of polyester/cotton (65/35) woven materialwere treated and tested as in Example 18 after five repeated washes for50 minutes at 45° C. in a 0.2% w/w aqueous solution of sodiumalkylethoxysulphonate. In this example, bleaching in the 3% aqueoussolution of sodium hypochlorite was carried out for 20 minutes at20°-25° C. The results are given in Table 3 which shows that thepolyester/cotton material withstands discolouration in the presence ofbleach and retains microbiological activity even after 5 launderingcycles in the presence of an anionic surfactant.

                  TABLE 3                                                         ______________________________________                                                              Surviving cells                                         Example Treatment     after 5 laundering                                                                        whiteness (%)                               ______________________________________                                        Control none          3E7         89                                          I       2% PHMB       6E2         80                                          19      2% PHMB + 1% citric                                                                         0           88                                          ______________________________________                                    

EXAMPLE 20

Example 14 was repeated execept that the cotton cloth was replaced bythe same amount of a 35/65 cotton/polyethylene glycol terephthalateblend woven piece and the oxalic acid solution was 0.5% by weight. Theresults are given in Table 4 below.

                  TABLE 4                                                         ______________________________________                                        Example                                                                              Treatment        Appearance                                                                              Whiteness (%)                               ______________________________________                                        20     0.1% PHMB/0.5% oxalic acid                                                                     white     80.99                                       J      0.1% PHMB        yellow    70.69                                       Control                 white     81.9                                        ______________________________________                                    

EXAMPLE 21

White cotton woven pieces (250 parts) was immersed in a 0.1% aqueoussolution of PHMB for 5 minutes at 20°-25° C. The cotton piece was thenremoved and rinsed thoroughly with water. The treated cotton was thenimmersed in 0.5% aqueous solution of oxalic acid for 5 minutes at20°-25° C. and again removed, squeezed, rinsed with water and dried. Thecotton was then padded with a 0.2% solution of a glycoluril resincontaining an acid catalyst, squeezed through a pair of nip rollers togive 60% pick-up and finally dried and baked for 10 minutes at 140° C.to cure the resin.

A similar cotton woven piece was prepared but omitting the oxalic acidtreatment. A length of untreated cotton was used as control.

5 cm² squares of the above cotton cloths (0.25 parts) were treated withsodium hypochlorite as described in Example 14 and the antimicrobialproperties were assessed as described in Example 18. The results aregiven in Table 5 below after subjecting to 0, 5 and 10 washing cycles asdescribed in Example 19.

                  TABLE 5                                                         ______________________________________                                                                       Whiteness                                                                            Surviving                               Example Treatment   No. of Washes                                                                            (%)    bacteria                                ______________________________________                                        21      0.1% PHMB   0          109    0                                               0.5% oxalic acid                                                                          5          116    0                                               0.2% glycoluril                                                                           10         126    0                                       K       0.1% PHMB   0          84.3   0                                               0.2% glycoluril                                                                           5          91.6   3.4 E2                                                      10         101.9  1.7 E2                                  Control None        0          97.4   4.3 E2                                  ______________________________________                                    

EXAMPLES 22 TO 24

White 35/65 cotton/polyethylene glycol terephthalate woven pieces (250parts) were immersed in an aqueous solution of 0.4% PHMB for 5 minutesat 20°-25° C. They were then removed, squeezed, rinsed in water anddried. Half of the pieces were then immersed in a 2% aqueous solution ofcitric acid for 5 minutes at 20°-25° C. and again removed, squeezed andrinsed in water.

After drying the treated pieces were padded through a 1% aqueous bath ofa curable resin, squeezed between nip rollers to give 60% up take, driedand baked for 10 minutes at 140° C.

The treated fabrics were then immersed in sodium hydrochlorite asdescribed in Example 1. The protection against yellowing conferred bythe citric acid is recorded in Table 6 below.

                  TABLE 6                                                         ______________________________________                                        Example Treatment     Citric Acid                                                                              Whiteness (%)                                ______________________________________                                        Control --            --         90                                           L       0.4% PHMB     --         82                                           M       0.4% PHMB     --         82                                                   1% epoxy resin                                                        22      0.4% PHMB     2%         90                                                   1% epoxy resin                                                        0       0.4% PHMB     --         85                                                   1% melamine resin                                                     23      0.4% PHMB     2%         88                                                   1% melamine resin                                                     P       0.4% PHMB     --         85                                                   1% urethane resin                                                     24      0.4% PHMB     2%         90                                                   1% urethane resin                                                     ______________________________________                                    

EXAMPLE 25

Example 15 was repeated except that the PHMB was replaced by the sameamount of chlorohexidine digluconate and the strong organic acid usedwas a 0.5% aqueous solution of malonic acid. The results are given inTable 7 below.

                  TABLE 7                                                         ______________________________________                                        Example     Treatment    Whiteness (%)                                        ______________________________________                                        25          0.1% chlorhexidine                                                            0.5% malonic acid                                                                          83                                                   Q           0.1% chlorhexidine                                                                         10.9                                                 Control     --           97.1                                                 ______________________________________                                    

I claim:
 1. A method of treating a textile material to inhibit microbialgrowth which comprises applying to the textile material a) an oligo- orpolymeric biguanide or salt thereof with an inorganic acid or an organicacid having a pK value above 4.5 followed by b) a strong organic acidhaving a pK value below 4.5 and free from any aliphatic or oxyalkylenechain containing 12 or more carbon atoms.
 2. A method according to claim1 wherein the strong organic acid has a pK value from 3.1 to 0.5.
 3. Amethod according to either claim 1 or claim 2 wherein the biguanidecontains at least two biguanide units of formula ##STR12##
 4. A methodaccording to claim 3 wherein the biguanide is a compound of formula IIaor IIb or III ##STR13## wherein n is 4 to
 15. 5. A method according toclaim 1 wherein the strong organic acid has the formula IV ##STR14##wherein R is halogen, C₁₋₆ -alkyl, C₁₋₆ -alkenyl, substituted C₁₋₆-alkyl, phenyl, substituted phenyl, nitrile, carboxy, a group OR³ or agroup R³ CO;R¹ and R² are, independently, hydrogen, halogen, amino,substituted amino, hydroxy, C₁₋₆ -alkyl, substituted C₁₋₆ -alkyl or Rand R¹ together with the carbon atom to which they are attached form analicyclic or heterocyclic ring; and R³ is C₁₋₆ -alkyl, substituted C₁₋₆-alkyl, phenyl or substituted phenyl; provided that R, R¹ and R² areselected to give a pK value below 4.5.
 6. A method according to claim 1wherein the strong organic acid has the formula V ##STR15## wherein R⁴is hydrogen, C₁₋₆ -alkyl, substituted C₁₋₆ alkyl, C₁₋₆ -alkenyl, phenyl,substituted phenyl or --COOH; andR⁵ and R⁶ are, independently, hydrogen,C₁₋₄ -alkyl or substituted C₁₋₄ -alkyl.
 7. A method according to any oneof claims 1 to 4 wherein the strong organic acid has the formula VI

    R.sup.7 --COOH                                             VI

wherein R⁷ is phenyl, substituted phenyl or the group --COOH.
 8. Amethod as claimed in claim 1 wherein the acid is malonic, maleic, citricor oxalic acid.
 9. A method as claimed in claim 1 wherein the textilematerial is rinsed with water after treatment with the strong organicacid.
 10. A method as claimed in claim 1 wherein the textile material iscellulose or a blend thereof.
 11. A method as claimed in any one ofclaims 1 to 10 wherein the textile material contains a binder or resin.12. A textile material treated with a) an oligo- or polymeric biguanideor salt thereof with an inorganic acid or an organic acid having a pKvalue above 4.5 followed by b) a strong organic acid having a pK valuebelow 4.5 and free from any aliphatic or oxyalkylene chain containing 12or more carbon atoms.